1. Field of the Invention
The invention relates to forming compressively stressed weld joints which are resistant to cyclic stressing and the corrosion enhanced by such cylic stressing. In one aspect, the invention is useful to form butt-welded T-joints of tubular members comprising an offshore platform useful for the production of oil and the like.
2. Brief Description of the Prior Art
The following comprises a prior art statement in accord with the guidance and requirements of 37 CFR 1.5, 1.97, and 1.98.
U.S. Pat. No. 3,512,811 discloses a pipe-to-jacket connector for offshore platforms, but does not appear to disclose prestressing the components prior to welding to form a compressively stressed weld joint.
U.S. Pat. No. 2,846,241 discloses a method of forming T-joints of improved strength by welding pipe, but does not appear to involve the inventive concept.
U.S. Pat. Nos. 3,882,654, 1,760,883, and 3,655,017 are exemplary of the art of forming weld joints of improved strength.
Weld joints on structures subject to cyclic mechanical stress such as members of offshore platforms are subject to a potential problem of fatigue or corrosion fatigue failure. The sites most subject to such potential problems are in or near the weld joints holding the members in T-configurations. In particular, the sites in the weld joints or the heat affected zone that extend farthest over the surface of a cylindrical tubular member to which the end of another cylindrical tubular member is butt-welded are most subject to such problems.
According to the process of this invention, such fatigue failure or corrosion fatigue failure problems which might affect weld joints holding offshore platform structural members and the like in T-configuration are mitigated or alleviated by fabricating the weld joints in compression stress.